Refractory application process and method

ABSTRACT

A refractory insulation on boiler tubes using studs circular in cross-section and having shoulders intermediate their ends with washers frictionally engaged on the studs sandwiching a mesh therebetween. The shoulder restrains movement of the first washer and mesh toward the substrate and the second washer retains the mesh from movement away from the substrate. A first insulation is applied to the substrate through the mesh and a second insulation layer is applied over the mesh to a predetermined thickness determined by the height of the studs above the shoulders. Pins can be welded to the tops of the studs and used to impale fibrous insulation.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a non-provisional patent application basedupon provisional patent application having Serial No. 60/336,266, filedNov. 2, 2001, and which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable

BACKGROUND OF THE INVENTION

[0003] This invention is applicable to the field of refractoryapplication and in particular to the application of refractory to boilertubes. The invention also concerns a novel stud for stud welding whichhas a shoulder spaced intermediate the ends of the stud to accommodatewashers used to position the mesh commonly used to reinforce therefractory applied to the boiler tubes. The invention specificallyinvolves a process for applying a refractory coating to boiler tubesusing a stud which is circular in cross-section and has a shoulder tolocate a reinforcing mesh a predetermined distance from the tubesurface.

[0004] The preferred stud is cylindrical and has a base leg which isattached at one end to the outside of the boiler tube and a shoulderlocated on the other end of the base leg. The shoulder is rounded on thetop to mate with the inner surface of a washer which is positioned overthe free end of an upper arm of the stud. The upper arm extends upwardlyfrom the shoulder and is aligned with the leg. The top end of the armpreferably is chamfered or rounded to facilitate application of thewashers. The preferred stud also has a completely rounded shoulder inthe form of a sphere to facilitate fabrication of the stud.

[0005] This invention has particular application to coal or gas firedelectrical generation plants in which steam heat is used to drivegenerating turbines. The outer surfaces of the boiler tubes are coveredwith an insulating refractory composition which is sprayed (gunned) ortroweled into place. To support the refractory, studs are welded ontothe tubes and an expanded metal mesh is placed onto the studs apredetermined distance from the tubes. A finish coat of insulation thenis troweled over the mesh to a predetermined thickness.

[0006] Studs presently used for this purpose are rectangular anddifficult to firmly weld to a boiler surface which may be partlycorroded or uneven. These studs are long and require the free end to bebent over the clip by hammering which often results in breaking theweld.

[0007] Pointed studs also have been used, but the clips used to locatethe mesh tend to slide down the pin toward the boiler tube when theouter layer of refractory is applied.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] The objects of the invention are achieved as set forth in theillustrative embodiments shown in the drawings which form a part of thespecification.

[0009]FIG. 1 is a fragmentary vertical sectional view of the presentinvention applied to a boiler tube;

[0010]FIG. 2 is a diagrammative drawing of the stud applied to a boilertube;

[0011]FIG. 3 is an elevational view of the stud;

[0012]FIG. 3a is a plan view of the mesh used in this invention;

[0013]FIGS. 4a-d are elevational views of modifications of the stud; and

[0014]FIG. 5 is a fragmentary vertical sectional view of anothermodification of the invention applied to a boiler tube.

[0015] Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF INVENTION

[0016] The following detailed description illustrates the invention byway of example and not by way of limitation. This description willclearly enable one skilled in the art to make and use the invention, anddescribes several embodiments, adaptations, variations, alternatives anduses of the invention, including what I presently believe is the bestmode of carrying out the invention. As various changes could be made inthe above constructions without departing from the scope of theinvention, it is intended that all matter contained in the descriptionor shown in the accompanying drawings shall be interpreted asillustrative and not in a limiting sense.

[0017]FIG. 1 shows the application of the invention to a boiler tube 10.The studs 111 are stud welded to the tube 10 using conventional studwelding techniques. The stud 111 is shown in more detail in FIGS. 2 and3 and comprises a leg portion 12 whose lower end 13 is welded to theouter surface of the boiler 10. The leg 12 is circular in cross-sectionand preferably is cylindrical in shape. The lower end 13 can bechamfered 13 a or flat and has a flux load 14. A shoulder 15 isconnected to the other end of the leg 12 and preferably is rounded tohave a spherical surface 16 for simplicity of fabrication. A top arm 17is aligned with the leg 12 and is connected at one end to the shoulder15 and has a free top end 18 which preferably is chamfered 18 a orrounded for ease of applying washers 30, as will be explained in detailhereinafter. The arm 17 is circular in cross-section and preferably iscylindrical in shape.

[0018] In the application process, the outer surfaces of the boilertubes usually are first cleaned and the studs 11 are welded on. Afterthe studs 11 are welded to the boiler tube 10, a washer 30 is passedover the stud end 18 and engages the top of the shoulder 15. The washer30 can be of any shape so long as it is sufficiently large so it willretain the mesh 31 which also is passed over the stud 11. The washer 30has a center opening 32 which is sized to frictionally slide over thestud arm 17 and resist movement on the arm 17. The opening 32 can be inthe form of an “X” cut in the washer 30. The washer 30 preferably has aconcave undersurface 33 around the opening 32 to mate with the studshoulder surface 16 to keep the washer 30 from moving past the top ofthe shoulder 15.

[0019] After the first washer 30 is applied to the stud 11, the mesh 31is positioned over the stud 11 and into engagement with the stud 30. Aretainer washer 30 a identical to the washer 30 is then passed over thestud 11 and into engagement with the mesh 31 The top washer 30 africtionally engages the stud arm 17 to retain the mesh 31 on the stud11.

[0020] Refractory insulation 40 is then sprayed (gunned) or troweledonto the tube 10 through the mesh 31. A final layer of refractory 41 maythen be troweled onto the top of the mesh 31. The layer 41 can be of aless dense, higher insulating refractory material. The thickness or“stand-off” of the refractory layers 40 and 41 are as defined by thedesign engineer. Thus, the stud 11 preferably is fabricated so theheight of the leg 12 and the shoulder 15 (plus the amount of the studconsumed in the weld) equal the desired thickness of the firstrefractory layer 40 and the height of the stud arm 17 equals the desiredthickness of the top refractory layer 41. The person applying therefractory can use the tops of the studs 11 as reference points inapplying the top layer of refractory 41 to insure it is of the specifiedthickness, thus avoiding excess, which adds to the cost of theinstallation, or a too thin layer which could result in failure of therefractory in use.

[0021]FIGS. 4a-d show other forms of the stud. FIGS. 4a-c show a flatshoulder 50 whereas FIG. 4d shows a stud having a shoulder 51 with onlythe top surface 52 rounded. All of the studs shown in FIGS. 4a-d areround in diameter.

[0022] Typical dimensions for the stud length A is 1¼″; the arm B is ⅜″;the height of the leg and shoulder C is ⅞″; the diameter D of the studarm is {fraction (3/16)}″ (0.1877″ 0.250″; and the diameter B of thestud leg is {fraction (5/16)}″ (0.250″ 0.3125″).

[0023]FIG. 5 shows the application of pins 55 which are welded to thetop of the studs 11 and used to impale a fibrous insulation 58 over theouter surface of the refractory 41. Speed clips 56 are positioned on thepins 55 at the free ends to retain the fibrous insulation 58. A metallictop sheeting 57 can be applied over the insulation 58 to protect it. Thetop sheeting 57 may be fastened to the tops of the pins 55.

[0024] In view of the above, it will be seen that the several objectsand advantages of the present invention have been achieved and otheradvantageous results have been obtained. REFRACTORY APPLICATION PROCESSAND METHOD (Our File TSF 81761U) Parts List 10. boiler 11. studs 12. legof studs 13. lower end of studs 13a chamfered 14. flux load 15. shoulder16. spherical surface of 15 17. top arm 18. free top end of 17 18chamfered 19. 20. 21. 22. 23. 24. 25. 30. washers 30a top washer 31.mesh 32. center opening of 30 33. concave under surface of 30 34. 35.40. refractory insulation 41. top refractory layer 42. 43. 44. 45. 50.flat shoulder 51. shoulder 52. rounded surgface of 51 53. 54. 55. pins56. speed clips 57. top cover 58. fibrous insulation

What is claimed is:
 1. A stud for applying refractory to a substratecomprising a leg having a first free end adapted to be stud welded tosaid substrate, a shoulder attached to a second end of said leg, and anarm having a free first end and a second end attached to said shoulderand aligned with said leg.
 2. The stud of claim 1 wherein the arm andleg are circular in cross-section.
 3. The stud of claim 1 wherein theshoulder is rounded on the top.
 4. The stud of claim 3 wherein theshoulder has a spherical outer surface.
 5. The stud of claim 1 whereinthe free end is chamfered or rounded.
 6. The stud of claim 1 wherein theleg and shoulder have a predetermined length equal to the desiredthickness of a first layer of refractory adapted to be gunned or trowledonto the substrate plus the amount of stud consumed by the weld, and thestud arm has a predetermined length equal to the thickness of a toplayer of refractory adapted to be trowled onto the substrate.
 7. Arefractory installation comprising: a substrate, a plurality of studswelded to said substrate, said studs having a shoulder intermediatetheir ends, first washers frictionally positioned on the studs andrestrained from movement toward the substrate by the shoulders, a meshpositioned on the studs and restrained from movement toward thesubstrate by the first washers, second washers frictionally positionedon the studs and restraining the mesh from movement away from thesubstrate, and refractory positioned between the mesh and the substrate.8. The installation of claim 7 including a second layer of refractorypositioned over the mesh and having a thickness substantially thedistance between the shoulders and the free ends of the studs.
 9. Theinstallation of claim 8 including pins positioned on the free ends ofthe studs and insulation impaled on the pins and retained thereon. 10.The installation of claim 9 including a protective cover over theimpaled insulation and fastened to the pins.
 11. The installation ofclaim 8 wherein the studs are circular in cross-section.
 12. Theinstallation of claim 8 wherein the stud shoulders are rounded on thetop.
 13. The installation of claim 12 wherein the first washers haveconcave under surfaces which mate with the stud shoulder rounds.
 14. Theinstallation of claim 11 wherein the free ends of the studs arechamfered or rounded to facilitate passage of the washers.
 15. Theinstallation of claim 8 wherein the stud leg and shoulder have apredertermined length equal to the desired thickness of the first layerof refractory on the substrate plus the amount of stud consumed by theweld, and the stud arms have predetermined lengths equal to thethickness of the top layer of refractory.
 16. The installation of claim8 wherein the substrate is boiler tubes.
 17. A method of applyinginsulation to a substrate including the steps of welding the studs ofclaim 1 to the substrate, frictionally engaging first washers onto thestuds against the shoulders, positioning mesh onto the studs whereby thefirst washers restrain the mesh from movement toward the substrate,frictionally engaging second washers onto the studs over the mesh torestrain the mesh from movement away from the substrate, applying afirst layers of insulting material to the substrate to a thickness ofthe mesh, and applying a second insulating layer to the first insulatinglayer to a thickness defined by the free ends of the studs.
 18. Themethod of claim 17 including the steps of positioning pins on the freeends of the studs, impaling fibrous installation onto the pins andrestraining the fibrous insulation on the pins.
 19. The method of claim17 wherein the substrate is boiler tubes.